Fifty short-eared owls were seen coming in off the sea at Titchwell, Norfolk, in October © Amy Lewis/BTO

With migration pretty much over, now is the time to reflect on what kind of autumn it has been. An autumn is often defined by the number of rare and scarce migrants that are found in the UK and as such this autumn will probably go down as one of the best ever.

Mid to late September saw two hurricanes sweep across the Atlantic, bringing North American waders and landbirds with them. A flock of 26 buff-breasted sandpipers gathered at Tacumshin, Wexford, on the 27th, whilst on the Isle of Scilly an early red-eyed vireo was joined by northern waterthrush, black and white warbler and Baltimore oriole.

One of the best autumns ever for scarce migrants saw a red-eyed vireo arrive on the Isle of Scilly © Joe Pender/BTO

After the storm came the calm, and with high pressure stretching all the way from the UK to North Africa, and the resulting light winds during early October, our departing summer visitors were provided with ideal conditions to move. Large numbers of hirundines, warblers, finches, chats and flycatchers were reported at coastal watchpoints, with records being broken at many sites. By the 4th 76,000 meadow pipits had been counted flying south at Spurn Point.

From the middle of October the wind turned more easterly and continued to come from this direction on and off through to the end of the month. Large numbers of finches, thrushes and geese began arriving but the most notable feature was the arrival of short-eared owls on the east coast. Fifty were seen to come in off the sea at Titchwell, Norfolk, on the 13th.

As September started, October finished, with some mouth-wateringrarities from the east and west being found. It all kicked off on the 1st when Britain's fourth Siberian blue robin was found dead on Foula, Shetland. The rest of the month saw the second eastern-crowned warbler, second rufous-tailed robin, fifth ovenbird, the ninth Siberian rubythroat and ninth and tenth scarlet tanager.

Whilst all this was happening, visible migration watchers were also kept busy as the finches just kept coming. Large numbers continued to move throughout October, mainly goldfinches, linnets, Siskins and redpolls, with a smaller but significant movement of crossbills.

Geese, like these white-fronted, were a highlight of early November © Chris Upson/BTO

As October gave way to November, geese became the highlight as pink-footed, greylag, white-fronted, tundra bean, barnacle and brent geese arrived in force. The BTO identification workshop is great for tips on how to separate grey geese in flight. Waxwings provided the first hint of what might turn out to be another waxwing winter; around two to three hundred arrived in early November.

The unseasonable temperatures may well have contributed to an impressive array of summer migrants lingering into November. Swallows, house martins, two or three redstarts, a pied flycatcher, a nightingale, several lesser and common whitethroats, at least half-a-dozen willow warblers, good numbers of wheatears, and around 30 records of swift, both common and the much rarer pallid were all still here.

As for the rarities, they keep coming too. The last week has seen blackpoll warbler, greater yellowlegs, sharp-tailed sandpiper, and at the time of writing, there is a veery on the island of Muck, Highland.

And, it's not over yet. As the temperatures fall in Eastern Europe and western Russia, we should see more of our winter visitors arrive, escaping the cold for the relative warmth of a British winter, birds like the Bewick's swan, pochard, goldeneye and smew, along with more geese and thrushes.

This week sees the 10th Conference of Parties of the Convention on the Conservation of Migratory Species of Wild Animals in Bergen. Populations of long-distance migratory landbirds are rapidly declining in the African-Eurasian flyway. Since 1995 and 2008, the populations of four summer-visiting birds declined by more than more than half, turtle dove (-70 per cent); wood warbler (-61 per cent); nightingale (-53 per cent); and yellow wagtail (-52 per cent), and during the last 25 years we have lost over half of our breeding cuckoos. (More on what the BTO is doing in Africa and its work on cuckoos.)

Low temperatures in the east have prompted large movement of barnacle geese © Jill Pakenham/BTO

With high pressure still dominant on the near Continent and the continuing southerly airflow, the weather conditions are essentially unchanged from last week. However, the temperature in eastern and northern Europe has begun to drop, triggering a large movement of white-fronted, tundra bean and barnacle geese. Skeins of these highly migratory waterbirds have been seen in a number of counties, with numerous records from inland sites as well as a more predictable glut of sightings at coastal locations.

The nightingale, one summer visitor who hasn't left yet © Edmund Fellowes/BTO

Waxwings continued to arrive on a broad front along the east coast, with some venturing as far inland as the West Midlands. We have a long way to go to match last winter's invasion though, as the BirdTrack reporting rate shows. The biggest arrival of the week featured blackbirds, with large numbers being seen at multiple sites along the east coast, presumably another product of the cooler weather further east.

A number of summer visitors are still hanging around, as is the case in most years, although the number and the diversity of species involved this autumn is impressive. During the last week there have been over 30 reports of swifts (both common swift and the much rarer pallid swift), seven wheatears, three house martins, two redstarts, a pied flycatcher, a nightingale, two or three willow warblers, lesser whitethroat, common whitethroat and several swallows.

Expect more waxwings next week © Edmund Fellowes

Not bad for mid-November, and likely to be at least in part attributable to the particularly mild autumn we've had in many parts of Britain and Ireland.

The weather is forecast to remain in a similar vein for at least the next four or five days, so we can expect more geese, more blackbirds and waxwings, and perhaps a major arrival of Bewick's swans.

Question of the week: When does migration come to a halt?

When we think of migration we think of our summer visitors leaving us to spend the winter in Africa, and the arrival of birds from further north coming to spend the winter with us. However, birds can be on the move throughout the year. During the winter months, periods of harsh weather will produce cold weather movements, as birds from both within the UK and from the Continent seek frost-free areas to feed.

Spring migration can start as early as the end of February and last until early June. In the case of waders heading for the Arctic tundra to breed, birds that arrived there early can often be on their way back whilst some of their congeners are still heading north.

During the summer months, failed breeders can begin moving south long before individuals that are in the process of successfully rearing young, whilst in many species, the young themselves leave later still.

In short, birds can actually make significant movements in any month of the year.

Starlings are on the move, so we'll soon see more of these spectacular sights © Jill Pakenham

It’s been a week of ups and downs. During the early part the winds had once again turned westerly and slowed migration down, and any movements involved small numbers of birds. After the weekend of easterlies waxwings continued to arrive. Around one hundred birds have now been seen on the east coast from Shetland to Kent.

Although most wildfowl failed to arrive, the first smew did © Edmund Fellowes

Wildfowl again failed to show. It’s still warm enough on the continent for them not to have to move. However, as always there will be individual birds that move no matter what and the first smew of the winter duly turned up, with single birds being seen in Cambridgeshire, Nottinghamshire, East Yorkshire and Lancashire.

By mid-week the winds turned southerly and promise to remain light and from this direction throughout the coming weekend and into early next week. There is also the promise of clearer skies for most of us.

This change immediately got finches on the move again, mainly goldfinches and chaffinches but also prompted skylark migration. Although the largest numbers were observed on the east coast, skylarks also migrate overhead further inland and can be seen moving in any county, particularly when the winds are light. This is definitely something to look out for this weekend. The clearer skies should also prompt the long-awaited woodpigeon migration.

During Saturday the winds might just turn south-easterly and provide the conditions for an arrival of black redstarts, particularly in the south and east. However, these birds can turn up almost anywhere even in land-locked gardens.

The last few weeks have seen a pretty steady arrival of siskins and redpolls. Both of these finches feed on the cones of alder and pines. With the wetter conditions earlier in the week a lot of cones will have closed and the seeds become harder to get at. In these conditions siskins and, more recently, redpolls turn to garden feeders, migrating from the wider countryside in search of food.

So what can we expect this weekend?

The last few days have seen more starlings on the move and this should continue through the weekend. As more and more of these birds arrive from Eastern Europe, so the size of the winter roosts will increase and the nightly spectacle of the pre-roost waves of birds become more impressive.

Could there be an arrival of black redstarts this weekend? © Jill Pakenham

Along with the black redstarts, robins could also be a feature with a noticeable increase in both the countryside and gardens. Although the movement of largely freshwater wildfowl has been pretty slow, that of seaducks has been quite impressive and anyone out by the coast this weekend should look out for lines of common scoter flying just above the waves, these are often accompanied by the rarer velvet scoter, whose white wing flashes give away their presence amongst their all dark cousins.

Question of the week: Why do some individual migrants stay further north whilst other individuals of the same species migrate much further south?

Using blackcap as an example, the majority of European blackcaps leave their breeding quarters and head south to North Africa where the winters are much warmer. However, there is an increasing number that undertake a very short movement and remain in northern Europe all winter long. For these birds this is a real gamble. If they experience a very hard winter with prolonged ice and snow many of them will likely perish. However, if the winter is mild and they survive they then have the advantage of being much closer to their breeding grounds next spring.

Being closer to the breeding grounds at the start of the breeding season means that they will undertake a much less arduous and hazardous migration, arriving back in good condition and earlier than those from further south. This allows them to take up the best territories with the consequent probability of a more successful breeding season.

The first waxwings are here © John Harding/BTO

As the migration of our summer visitors comes to a close, it's easy to think that autumn migration also comes to a close. Nothing could be further from the truth. Migration watchers in early November can be rewarded with some of the most spectacular bird migrations of the year.

At this time of the year migration is very much influenced by the weather in northern and eastern Europe, with temperature all important.

Falling temperatures on the continent will mean an influx of golden plover © Tommy Holden/BTO

A sudden freeze will see berry crops fall and waterbodies ice over, prompting cold-weather movements for thrushes (redwings, fieldfares, blackbirds, song thrushes and ring ouzel), finches (siskins, redpolls, linnets, chaffinches and bramblings), larks (skylarks and woodlarks), pigeons (woodpigeons and stock doves) and wildfowl (ducks, swans and geese).

So far this autumn with temperatures higher than normal we have seen very little of this. The daytime temperature in eastern Europe, however, is forecast to drop to near freezing this weekend, so we could see an arrival of pochard and goldeneye, along with a small arrival of Bewick's swans. [Editor's note: Slimbridge, Autumnwatch's hosts for the next four weeks, is one of the UK's best sites for Bewick's.]

Up until now there hasn't been a need for these birds to move. Check out the BirdTrack reporting rate for goldeneye.

Any cool crisp day with light winds, particularly from the east, over the next couple of weeks should prompt a big movement of woodpigeons, with flocks often tens of thousands strong heading south-west. You don't have to be on the coast to observe this migration spectacle, big flocks can be seen flying over land-locked counties too.

A sudden freeze will see blackbirds on their way © John Harding/BTO

The first waxwings of the autumn have been seen, with a flock of 20 birds being found in Stromness, Orkney, and three seen on Lewis, Outer Hebrides. It's too early to say whether it will be a waxwing winter, but with the drop in temperature on the continent this weekend we might see a few more arrive. At this time of the year waxwings generally arrive in the north and work their way south as berries become harder to find.

Flocks of lapwings and golden plovers on the move are a sure sign that the ground is frozen on the continent, so falling temperatures there could cause an influx of these winter field inhabiting waders.

Question of the week: Is it true that some birds reduce internal organs to compensate for the extra fat they carry for migration?

This is absolutely true and is illustrated perfectly in a passage from Ian Newton's excellent book, Bird Migration. Organ reduction has been found in a number of migratory species, including pied flycatchers, willow warblers and swallows. However, extreme changes were found in bar-tailed godwits killed accidentally in Alaska as they hit a radio tower, just after take-off on a presumed trans-Pacific flight of at least 10,400km to New Zealand.

These Alaskan godwits had some of the highest fat contents recorded among birds, comprising 55 percent of total body mass. They also had relatively large breast muscles and heart (exercise organs), but very small gizzard, liver, kidney and gut (digestive organs). They had largely dispensed with parts of their metabolic machinery that were not essential during flight, presumably converting them to other tissue.

On arrival at their migratory destinations, birds rebuild their digestive organs, so that they can once again feed efficiently.

The blackcap, marooned on Fair Isle © Mark Taylor/BTO

There has been a north/south divide this week, and the further north you go the greater the divide. The very strong south westerly winds have remained gale force for most of the week in the very north of Scotland and the northern isles, grounding large numbers of geese and swans and effectively bringing any migration there to a complete halt. At present there are around 30 blackcaps on Fair Isle, Shetland, that will be unable to leave until the wind drops considerably.

Further south the winds have been much lighter and at time movement has been impressive. The first large arrival of starlings occurred at the beginning of the week, along with impressive numbers of finches, linnet being the most numerous of these, accompanied by smaller numbers of goldfinches and chaffinches.

Ring ouzels stop over in the UK on their way to Africa © Tommy Holden/BTO

Winter thrushes continue to arrive whenever conditions allow. While the redwings and fieldfares may not go much further than the UK, the ring ouzels that have arrived with them this week will be making their way to North Africa to spend the winter months in and around the Atlas Mountains. Late October and early November can be a great time to catch up with this enigmatic thrush, some even turn up in gardens at this time.

The first of the Bewick's swans have begun to arrive © Jill Pakenham/BTO

The strong winds have held up a few of our departing summer visitors but for the 30 swallows that are still in the Christchurch Harbour area in Dorset the higher than average temperatures for the time of the year will mean that there will still be plenty of aerial insects around to feed-up on ahead of the long journey south.

The first of the Bewick's swans from the Arctic Russian tundra have begun to arrive on the east coast. If the winds are as light as they are forecast to be this weekend, we could see the arrival of more of these wild swans, along with further arrivals of starlings, goldcrests and woodcock, the latter two nearly always seem to arrive at the same time.

Question of the week: Do all birds migrate in flocks?

The simple answer to this is no.

A lonesome migrant: the corncrake © Edmund Fellowes

Many of our birds will undertake migration alone. Warblers, flycatchers, chats and birds like quail, corncrake and cuckoos undertake their huge migrations to Sub-Saharan Africa entirely alone. However, for others, flocking is the norm, thrushes, starlings, finches and pipits all migrate in loose flocks and utter contact calls to keep these flocks together.

For most wildfowl, not only is flocking the norm, migrating with the rest of your family is too, making this time of the year a good time to get an indication how good a breeding season birds like whooper and Bewick's Swans have had.

It's unclear why different birds use differing migration strategies. Warblers in the UK are mainly nocturnal migrants, whilst the North American warblers migrate during daylight hours. However, for our summer visitors that cross the Sahara, a night crossing might be much more beneficial than one undertaken during the searing heat of the day. We do know that one of our satellite tagged cuckoos did actually cross the desert during the day, so we still have quite a lot to learn about birds on migration. To see where our five cuckoos (including Martin and Chris) are now visit our special tracking website.

The whinchat, still around on Fair Isle © Ron Marshall/BTO

In a departure from the normal migration blog we thought it would be good to give you a flavour of what Nick and I have been up to this week.

Last Friday we arrived on Fair Isle, a three miles by one mile island roughly mid-way between Shetland and Orkney, for a seveniday stay at the world famous Fair Isle bird observatory. Our reason for being here? To experience for first-hand migration through and over this magical island.

We had only just left the airstrip when we were shown our first Fair Isle speciality, the very rare lanceolated warbler. Unfortunately for the bird and for us, it had been found dead just minutes before. This is probably the sad fate of most wind-blown vagrants that find small islands.

By Sunday, the thrush numbers had halved but bramblings and snow buntings took their place, and rather interestingly, given the wintry flavour, several wheatears also turned up, sharing the island with at least three whinchats.

The chiffchaff, a sign that summer isn't quite over © www.grayimages.co.uk/BTO

Summer wasn't quite over though. On Monday and Tuesday 30 blackcaps and a few chiffchaffs arrived, most of them ignoring the crops and crofts in favour of the impressive cliffs.

If the birds gave a taste of summer, the weather on Wednesday was straight out of the Arctic north. Gale force north-westerly winds and snow showers were the theme for the day. These seemingly impossible conditions, which grounded all flights and sailings from the island, triggered a large movement of greylag geese. 700 were counted passing over the island on their way south from Greenland.

It was on Wednesday afternoon that we heard about another very rare bird, a Siberian rubythroat, a stunning male with full 'rubythroat', had been found on mainland Shetland, some 30 miles north of Fair Isle. This bird normally winters in northern India.

As well as coming to Fair Isle to experience migration as it happens, we wanted to experience some of the rare birds that Fair Isle is famous for. So far we'd managed to see a Blyth's reed warbler and olive-backed pipit, both of which should have been with the rubythroat in India. Add to that list, two or three common rosefinches, a bluethroat, a barred Warbler and a Siberian chiffchaff.

Thursday dawned calm and sunny. These still conditions were the cue for birds to leave. By lunchtime it was clear that they had done just this, and we had the quietest day of the week so far. So with our migration counts completed we began to think about the rubythroat and wonder whether we might just be able to get off Fair Isle and catch a sight of this almost mythical bird.

Pochard, on the way next week © Jill Pakenham/BTO

What unravelled over the next hour proved to be the start of a real adventure, and un-scheduled flight off the island and us seeing a bird that we both have only ever dreamed of seeing before.

Even here though we continued to log migration. Over one hundred golden plovers moved overhead, and 15 blackbirds came to roost in the rubythroat's garden.

With the winds due to turn south-easterly, next week we should see winter wildfowl, particularly pochard and goldeneye arrive in force. We'll be back in Norfolk in time to witness these very smart looking ducks turn up.

Have you noticed any birds leaving yet? Anything unusual or surprising? As always, post a comment below.

The hawfinch, arriving this week © Edmund Fellowes/BTO

Strong westerly winds have dominated the weather this week. As a consequence songbird migration has been very slow. The strong winds did, however, blow Leach's petrels into coastal waters along the west coast. Reasonable numbers were seen at several locations - particularly in the northwest - over the weekend.

When the wind has dropped slightly birds have taken the opportunity to move. With the majority of the swallows having left already it's been the finches that have been the most obvious and of these the goldfinch has lead the way, 1,325 moved south over Spurn in East Yorkshire, on Monday.

The fieldfare: a herald of autumn © John Harding/BTO

These finch movements have included a smaller number of linnets, redpolls, siskins, the first few bramblings and, of particular note, crossbills and a handful of hawfinches. Judging by the rise in the number of these birds spotted on the east coast, these are like to have an origin further north and east of the UK. [Editor's note: Autumnwatch was at Spurn in full force earlier this week. Watch Friday's show to see why it's such a Mecca for bird lovers.]

House martins now dominate the hirundine movement. As the winds drop over the next few days we should see a big exodus of this species.

The last few days has also seen the arrival of more redwings and a smaller number of fieldfares. No doubt this is a result of the conditions that also brought the hawfinches and crossbills. The thrushes have been very quick to push inland and many counties have recorded their first of the autumn in the last few days.

What to look out for this weekend

The wind is due to turn south and southeasterly over the weekend. While it will be moderate in the south, it's going to be quite strong in the north. This will mean that it could be quiet few days on the wildfowl front but we could see the first large influx of winter thrushes, goldcrests and the first movement of woodcock, particularly on the east coast.

Question of the week: Why do birds sing in autumn?

It might seem illogical for birds to sing in autumn; after all, very few of our songbirds will be nest- building or egg-laying over the next four months or so, so why would males bother trying to attract attention now? There are, however, some interesting ecological and physiological explanations.

Why do robins sing in the autumn? © Jill Pakenham/BTO

Some species, like robins, sing to establish and defend winter territories. This ensures that individuals have somewhere to feed during the difficult months ahead, and are in the best possible condition come the start of the breeding season. From a physiological perspective, it seems that the post-breeding moult of some of our songbirds, such as starlings, causes increased testosterone levels, which may in turn trigger autumnal singing.

This effectively means that autumn is the start of the breeding season for these species, but inclement weather and shortening day-length then suppress further breeding activity until spring. Research into autumn-singing robins, however, suggests that their testosterone levels are not particularly high at this time of year, so testosterone is not the only answer. Furthermore, autumn robin song is quieter and of a different quality to that of spring.

A number of migratory and flocking species also sing in the autumn. There is even some evidence that female and juvenile birds of some migratory species also sing at this time. One possible explanation is that these birds are singing to maintain social status within the flock. A weak, quiet song, termed 'subsong', can also be given by lone migrants; its role isn't entirely clear but could be part of the song-learning process for young males, prior to their first breeding season the following spring.

Have you noticed any birds leaving yet? Anything unusual or surprising? As always, we'd love to hear, so post a comment below.

Whooper swans were part of the exodus from the north this week © Jill Pakenham

As we were basking in summer-like sunshine, winter arrived in Greenland and Iceland, where heavy snow and freezing temperatures were very much the order of the day. This was the trigger for Greenland wheatears to leave there. Monday saw a large wave of these birds pass through the UK, with at least 250 birds were counted at Spurn Point alone.

This peak is also reflected in the BirdTrack national reporting rate. It's amazing to think that some of these birds breed in western Alaska and still migrate to Africa for the winter, crossing Greenland, Iceland and the western edge of Europe on the way. Around the size of a robin, they will fly 10,000km (6,000 miles) before they reach sub-Saharan Africa.

Wheatears: on the move from Iceland and Greenland © www.grayimages.co.uk

Birds also exiting the north included whooper swans, geese (mainly greylag, pink-footed and brent, with smaller numbers of white-fronted and barnacle) and dabbling ducks such as wigeon and teal.

Most swallows have already made their final big move south and reports of this species have already dropped dramatically. House martins normally leave a little later than swallows and they've certainly been seen in larger numbers this week.

So what can we expect over the weekend?

Leading into the weekend the winds will turn north-westerly and for a while come straight out of Greenland and Iceland, providing ideal conditions for swans, ducks and geese to leave, so we should see a significant arrival of whooper swans, greylag, pink-footed, barnacle and pale-bellied brent geese and wigeon and teal. We could also see the first big arrival of Icelandic redwings.

Question of the week: Why are some migrants very tame?

Every year there are stories of migrants like goldcrests that seem unusually confiding when encountered at coastal sites. From time to time much rarer migrants hit the headlines because of their tameness.

Famous examples from the 1980s included both baillon's and little crakes (in Sunderland and Sussex respectively) and an upland sandpiper on the Scillies, and more recently, a steppe grey shrike in Lincolnshire in 2008. All these birds were watched at extremely close range; the upland sandpiper was even seen to take a worm from a birdwatcher's mouth!

Sheer exhaustion is likely to be one of the reasons that can make migrants particularly tame. Birds use a huge proportion of their energy reserves when migrating. Hence their number one priority on making landfall is to find food, even if that means being less wary of predators. When humans provide food, tired migrants will often take advantage of the free meal much quicker than they would under normal circumstances.

Many vagrant birds that reach our shores come from places with low human population density and the fact that such species therefore don't associate humans with danger is another reason often given for tame behaviour. Finally, birds that have been disorientated by bad weather and attracted to lighthouses or lights on ships may be slightly dazed; this could also account for tameness.

Have you noticed any birds leaving yet? Anything unusual or surprising? As always, we'd love to hear, so post a comment below.

Black terns have been moving en masse earlier this week © Andy Mason

It's very much been a week of two halves. The early part of the week saw large numbers of common migrants on the move and a huge movement of black terns through the country, with flocks in excess of 100 birds being counted on a couple of inland waterbodies. The latter part of the week was however much quieter.

Swallows and house martins dominated the visible migration during the first few days of the week, with smaller numbers of meadow and tree pipits, pied and yellow wagtails, and goldfinch, siskin, redpoll and chaffinch all moving.

The grey wagtail: bang on cue this year © Edmund Fellowes/BTO

A small number of grey wagtails were also counted, which is bang on cue for the first autumnal movements of this species.

As the wind turned south-easterly birds from the east were found, and included a few wrynecks, red-backed shrikes and icterine warblers, along with the fourth Blyth's reed warbler for Portland Bill in Dorset.

Eastern visitor: the wryneck © Jill Pakenham/BTO

It has been a much quieter week for rarities. However, a semipalmated plover, the find of the autumn so far, was discovered on Ventry Beach, Kerry. This is the fifth record of this North American species for Britain and Ireland and was probably another hurricane Katia blown waif. The east is also well represented with up to 12 pallid harriers. Only a decade ago this was a mega rarity.

What can we expect?

With high pressure settled over us for at least the next four to five days, visible migration counts will be at a premium. This doesn't mean that migration has come to a halt, migrants will still be on the move and probably in high numbers, it is just that they will be flying over at a much higher altitude making them near impossible to see. However, with the warm southerly airflow associated with the high pressure, coming from south-eastern Europe we could be in for a surprise from this direction. Please let it be a Tengmalm's owl in Norfolk!

Question of the week: What happens to a lost migrant?

The British Isles is well situated geographically to receive vagrant birds (birds that don't normally occur here). This has been illustrated perfectly this autumn with the arrival of several North American landbirds and the largest-ever arrival of pallid harriers from Eastern Europe and western Russia.

The North American birds arrived here in the wake of hurricane Katia, blown off course from their normal migratory route (which is often over 100km offshore over the western Atlantic) from North to South America. The predominantly westerly airflow across the Atlantic makes it very unlikely that these birds will ever get back to North America.

Having rested and fed these birds are likely to continue on their migratory trajectory, albeit on the wrong side of the Atlantic. Initially this might take them in a southerly direction but eventually they will turn south-west, the direction that would enable them to make landfall in South America. They will most likely perish in the Atlantic Ocean.

Having said that, it's suspected that individuals of some species, waders and waterfowl in particular, don't attempt to re-cross the Atlantic and simply continue their annual migrations on this side of the pond, often with flocks of similar species. Many such vagrants lead a relatively lonely existence, as they are unlikely to encounter members of their species ever again.

The prospects for birds arriving from the east seem to be rosier. Having rested, ringing evidence has shown that some of these birds are able to reorient and resume their migration trajectory. A rustic bunting ringed on Fair Isle in June 1963 was recovered on the Greek island of Chios four months later, suggesting that it had reoriented eastwards.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

The redwing, a sure sign winter is round the corner © John Harding/BTO

Many of our summer visitors have taken advantage of the relatively settled conditions since hurricane Katia lashed our shores to begin the long journey south. The weekend saw the biggest movements of swallows so far this autumn, with an estimated 40,000 being counted at one south coast watchpoint in just a few hours.

The settled conditions have been perfect for observing visible migration, counting flocks of birds as they fly overhead, and there has been an obvious increase in the numbers of meadow pipits and wagtails, with both pied and yellow wagtails featuring more as the week has progressed.

The finches, like this siskin, have been moving in earnest © Johh Harding/BTO

Finches are also beginning to move in earnest, with siskin being the most obvious; we have noticed an increase in the number of siskins flying over the BTO headquarters here in Norfolk, which is reflected in the BirdTrack reporting rate across the country.

Redpolls, goldfinches and linnets are also on the move in smaller numbers, particularly along the east coast. The Met Office is forecasting a hint of southeasterly in the wind for this weekend which could well trigger a larger movement of all of these species. If the weather report is correct, conditions could be perfect for observing visible migration, particularly in the east and south, whilst further north the forecast showers could result in localised falls of pipits, wagtails and finches.

Pink-footed geese © C Mills/BTO

Small flocks of geese have also been a feature of the week and have mainly involved pink-footed geese and brent geese, a real sign that winter is just around the corner, and as if to confirm this, the first redwings and fieldfares have arrived in the north. (Editor's note: there's been a few sightings of fieldfares on our Facebook page.)

So what might we see during the next week?

Geese and finch numbers will continue to build, visible migration ought to continue in the same vein as this last week, and we should also see, and more importantly hear, redwings arriving. Now is a great time to get out in the garden after dark and listen for these largely nocturnal migrants going over, uttering their distinctive 'tseep' calls.

It will probably be much quieter on the rarity front with the more settled conditions, but we are heading into the last week in September, traditionally the time when great rarities from the east can occur. Thinking (too?) positively, I'd like a bimaculated lark on Blakeney Point, whilst Nick is angling for a pallas's sandgrouse on Scolt Head Island!

America is still providing most of the rarity interest at the moment though, and not surprisingly the west of the country received the lion's share. The Isles of Scilly have played host to four American landbirds, with northern waterthrush, black-and-white warbler and Baltimore oriole all joining the red-eyed vireo that was present last week.

The north hasn't been completely left out of this American bonanza though. A swainson's thrush and an American buff-bellied pipit were found on Shetland and a sandhill crane in Aberdeenshire.

Question of the week: What makes a rarity rare?

Silly question? Not really, because there are several factors involved in determining how rare a particular species is in a UK context. We're talking about migrants as opposed to rare breeding species (though you probably worked that out from the title of the blog!) - and it's not just about numbers.

As you might expect, breeding distribution relative to the UK plays an key role. As a rule of thumb, migratory species that breed in northern Europe and western Siberia are more likely to turn up here than those breeding further afield. Population size is also important. Even though species like roller, ortolan bunting and aquatic warbler are strong migrants and breed not that far away, all three have suffered serious population declines and have become increasingly rare in the UK in recent years.

Migratory tendency matters too. Take last week's red-eyed vireo for example. Although this species breeds in North America, there are more than 150 records in the last 50 years. In contrast there have been just eight crested larks over the same time period, despite the fact they breed in France, Belgium and the Netherlands.

The difference is that red-eyed vireos migrate to South America every autumn (or should we say 'fall'?) putting them at risk of displacement by bad weather, whereas your average crested lark starts to get a bit panicky if it leaves the field where it hatched. OK so maybe that's a bit of an exaggeration but you know what we mean...

Finally a species' habits have an impact on its rarity status. You won't be surprised to hear that seabirds spend much of their time at sea, making them naturally harder for land-loving birdwatchers to find and identify than their terrestrial counterparts. And some birds, such as Locustella warblers, are just naturally very shy and furtive... many a birdwatcher's autumn conversation has turned to the question of just what volume of such birds pass through undetected each year.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

The red-eyed vireo arrived after a journey of 5,000km © Joe Pender

At this time of the year, storms can often bring birds to Britain and Ireland from far-flung places, and as the tail-end of hurricane Katia lashed our western shores earlier this week, it brought transatlantic migrants with it. Over 60 buff-breasted sandpipers arrived, with a single flock of 14 seen on Loop Head in County Clare, Eire.

They were not alone, over 30 pectoral sandpipers and a single solitary sandpiper were also found. The latter sharing the Isles of Scilly with the only American landbird to arrive, a red-eyed vireo, which was found on St Mary's on Tuesday. This bird, about the size of a dunnock, will have travelled at least 5,000km to get here.

The pectoral sandpipers, a transatlantic migrant © Ashley Fisher

So what effect has this had on migration here? The strong winds during the early part of the week effectively brought migration to a halt for many of our smaller birds. Now that the winds have died down, migration will again be in full swing, with hirundines (swallows and martins), pipits and finches making up a large part of any movement. The BirdTrack reporting rate for swallow shows this increase well as birds are counted at migration watchpoints.

The red-backed shrike might arrive on in the east Neil Calbrade/BTO

Most of the action this week has been in the west but with the light south-easterlies forecast for Friday, the eastern side of the country could be the place to be, with wryneck and red-backed shrike a strong possibility on an early weekend walk. By Saturday lunchtime and in to Sunday the strong westerlies are due to return, swinging focus back to the west, where we could have a repeat performance of the early part of this week.

Question of the week: What causes falls of migrants?

During ideal conditions for migration (light winds and clear skies) migrant birds have little problem following a predetermined heading towards where they want to migrate to. However, for long distance migrants the conditions can change during their migration and they can be drifted off-course by the prevailing winds and find themselves over the open ocean.

Once over the ocean it seems that a migrant bird is unable to compensate for the original drift that got it there in the first place, and they continue in the direction that the wind is taking them until land is found. Or they perish in the sea, as many migrants in this situation must do.

Once on land, a migrant is able to once again re-orientate and head off on the original course, albeit sometimes in a very different part of the world, the red-eyed vireo on the Isles of Scilly this week is a prime example of this. (This was beautifully caught on camera by mpgoodey, a member of our photo group)

Of course large numbers of birds can be caught-up in bad weather events and can literally fall out of the sky once land is found, resulting in large falls of a variety of species seeking shelter and food. One of the most famous falls occurred in September 1965 on the east coast, involving 15,000 common redstarts, 8,000 northern wheatears, 5,000 pied flycatchers, 3,000 garden warblers and many others.

Birds can also occur in falls when they encounter heavy rainfall and will drop from the sky to seek shelter until the rain has passed.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

Manx shearwater © Joe Pender/BTO

The westerly gales that have been battering the coasts from the Cornwall to the Outer Hebrides have resulted in some spectacular seabird counts, in particular the rarer shearwaters. During the week, over 7,000 sooty shearwaters, 2,500 great shearwaters and 600 Balearic shearwaters, the latter globally listed as critically endangered, were counted off south-west Cornwall, south Devon and south-west Ireland.

Among these were also numerous grey phalaropes, leach's petrels and sabine's gulls. Large numbers of gannets and, as predicted in last week's post, Manx shearwaters were also seen in good numbers. Some newly fledged young of the latter struggled with the stormy conditions and 491 found themselves 'wrecked' on Newgale Beach in Pembrokeshire. The BirdTrack reporting rate shows nicely the increase of observations of this species.

Gales brought a dozen buff-breasted sandpipers to our shores © Joe Pender/BTO

As was to be expected, the fast tracking Atlantic gales brought North American waders with them and over a dozen buff-breasted sandpipers arrived on our shores, with the Isles of Scilly hosting five of them, again the west received the lion’s share but birds have been found at Rye Harbour in East Sussex and Titchwell in Norfolk.

Despite the windy conditions swallows and meadow pipits have been a feature of visible migration watches. Over 12,500 swallows were counted heading south at Spurn Point on Saturday, with almost 8,000 meadow pipits heading in the same direction yesterday.

Swallows gettting ready to leave © Paul Stancliffe/BTO

The first large finch movement was also observed here yesterday with over 600 siskins also heading south.

With the wind set to increase again from the west on Sunday, observers on the west coast could be in for another weekend seabird fest, whilst in the east, finches and pipits should make the most of any lull in the windy conditions.

Question of the week: How do birds cope with the risks of migration?

The very act of long-distance migration has to be one of the most arduous and dangerous activities that a bird undertakes, so what can they do and indeed do they do to minimise the risks associated with long-distance migration.

For those migrants that undertake long sea or desert crossings, it’s essential to store enough fat deposits to fuel these flights and many of our smaller birds spend up to three weeks feeding up and accumulating fat reserves before their departure, some will have more than doubled their normal weight.

Setting off in optimum conditions also helps to minimise the risk of being downed or blown off-course and also maximises the stored fat reserves. If birds encounter worsening conditions, many will make landfall and rest-up and feed-up until conditions improve.

Some birds migrate primarily at night, reducing the risk of predation by diurnal raptors. Flying in the cooler night air also reduces drag and minimises the use of the stored fat reserves.

Now is a great time of year to see the hobby © Jill Pakenham/BTO

If you let on that you have an interest in, or any knowledge of, birds, someone somewhere will ask which species is your favourite. For as long as I can remember my answer has been hobby. This is an extremely acrobatic, migratory falcon, which makes its living by catching some of the most manoeuvrable prey items on offer: swifts, swallows, martins and dragonflies!

Hobbies will tackle easier prey when the opportunity arises; earlier this week I was fortunate enough to witness a breathtaking attack as a hobby stooped from a great height at a greenfinch - fortunately for the greenfinch, it was able to take evasive action at the very last second.

Other migrants on the move at the moment include seabirds such as Manx shearwater and Arctic skua, both entering their peak southbound passage periods right now. Weather conditions over the next two or three weeks will play a part in determining how many are seen from land; onshore winds are usually needed to bring these pelagic (sea-faring) species close enough to the coast to be seen in large numbers by birdwatchers.

Whinchats are on the move © Mike Weston/BTO

On the songbird front, the BirdTrack reporting rate shows that whinchats are on the move; whilst they will be most numerous at coastal watchpoints, they can occur on patches of rough, open ground anywhere in the UK, so it's worth keeping an eye out for these intricately-patterned chats. Sadly whinchats are one of a suite of long-distance migrants that are suffering long-term population declines; several conservation organisations are trying to find out what is causing these declines, both here and on their wintering grounds in Africa.

The first batch of unusual migrants have turned up on Fair Isle, a famous migration hotspot that Paul and I are lucky enough to be visiting this October - we're already feeling like kids on Christmas Eve! Perhaps we should have been there last week though - as well as their second highest ever count of wrynecks (a whopping 19 on 24 August!), Fair Isle Bird Observatory also recorded two scarce 'hippos' in one day on 26 August: booted and melodious warblers (both members of the Hippolais genus of warbler, rather than enormous herbivorous African mammals).

Question of the Week: How do birds find their way? (Part 2)

In last week's brief look at birds' ability to detect the earth's magnetic field and use it as a navigational aid, we mentioned that having an internal compass is no use if you don't have a road atlas. Fortunately for birds, there's a ready-made road atlas right above their heads, in the form of the stars at night and the sun during the day. Birds are able to read these 'celestial cues' to help them ensure that they stay on course.

Of course the problem with any visual cue is that you need to be able to see it; any form of cloud cover can obscure the stars, and for day-flying migrants, thick fog or heavy cloud will make it very hard to detect the location of the sun. Exactly how different weather conditions can affect birds during their migration will be the subject of a future Question of the Week.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

The intricately-patterned wryneck © Jill Pakenham/BTO

Easterly winds and drizzle dumped a scattering of migrants along the east coast this week. On a wander down the three-mile long shingle spit of Blakeney Point in Norfolk on Tuesday I was quite surprised to find that the most numerous warbler species was the usually unobtrusive garden warbler, while willow warblers and whitethroats were rather few and far between.

Whimbrel are at their peak right now © Ron Marshall/BTO

Flycatchers and chats are on the move too. Pied flycatchers have been in evidence at various locations, both coastal and inland, as have wheatears.

Late August is also the peak time for several migratory species of wading birds. Just last week, a flock of seven whimbrel flew over me in the unlikely location of a patch of Forestry Commission land in Thetford Forest, highlighting the broad front across which many species migrate. The BirdTrack reporting rate for whimbrel shows a really clear pattern of two peaks of sightings, the first in May and the second right now. One of the best ways to detect this curlew-like wader as it passes overhead is its piping, whistled calls, which you can listen to here.

Question of the week: How do birds find their way? (Part 1)

How migratory birds are able to navigate their way to and from their breeding grounds, often across vast distances, is one of the enduring questions posed by the natural world. We think that there are three key parts this mystery: birds' use of magnetic, celestial and visual cues. Over the next few weeks we'll take each of these in turn and try to explain a bit about how it works.

First up, magnetic cues. There's good experimental evidence that some species of bird are able to detect the Earth's magnetic field. Crystals of an iron-based mineral called magnetite have been discovered in the brains of pigeons, amongst other species, and these are thought to give the bird the ability to sense the polarity of the Earth's magnetic field.

An 'internal compass' is a pretty handy tool to have if you're a migratory bird, allowing you to migrate in roughly the right direction even if you can't see exactly where you're going. It is no good having a compass without a map though and we'll talk about the avian equivalent of a road atlas in a later post.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.

Sedge warbler migration is now at a peak © Dawn Balmer/BTO

Last week it was the swifts, this week sedge warbler migration is at its peak. Large numbers of this intricately-marked warbler are passing through watchpoints on the south coast right now. This was illustrated perfectly at a bird ringing site on the Pett Level in East Sussex this weekend. A team from the BTO joined the regular ringers to help get a handle on the huge volume of birds leaving the country at the moment. Of more than 2,000 birds caught and ringed, about 25% were sedge warblers. The Birdtrack reporting rate shows perfectly how this species is flooding out of the UK.

Common terns have become more obvious offshore © Andy Mason/BTO

Other species that were well represented were willow warblers and whitethroats, while sand martins (our earliest departing member of the swallow family) far outnumbered swallows at the evening roosts.

Juvenile cuckoos are starting to leave © Andy Musgrove/BTO

Common terns have become more obvious offshore as they make their way south in migrating flocks, 2, 530 were counted past Spurn Point on 16 August. Flocks of migrating terns flying just above the waves determinedly heading south provide one of the greatest spectacles of autumn migration. However, this week the terns at spurn were eclipsed by swallows; 7,500 were counted heading south over there on the same day. Over the next few weeks the number of these two species should increase as more and more begin their migrations.

The first juvenile cuckoos are also beginning to appear at coastal watchpoints. It's interesting to think that some of these could be the youngsters of the BTO satellite tagged cuckoos that are being followed to their wintering grounds which are already south of the Sahara.

Question of the week: What triggers migration?

It's largely recognised that there are two types of migration. Obligate - controlled by genetics - and facultative - controlled by external factors such as local weather conditions. For birds such as swallows, terns and cuckoos, it is obligate migration that we are interested in.

Change in day length is an important factor in the timing of migration for obligate migrants, and coupled with the genetic influence, can give greater year-to-year consistency in the timing of migration in individual species. For example, British swifts largely tend to leave the country during the first week of August.

Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.